Instantaneous Start Research Articles

The Effects of Liquid Density and Impeller Size with Volute Clearance on the Performance of Radial Blade Centrifugal Pumps: An Experimental Approach

This study was carried out to experimentally investigate the effect of impeller size with volute clearance and liquid density on the performance of radial blade centrifugal pumps. Three impeller sizes of 121.54mm, 109.38mm and 97.23mm with respective volute clearance of 6mm, 12mm and 18mm were considered, and five different liquid blend which comprise of water, two liquids that are denser than water and two other liquids that are less-dense than water (with respective liquid densities of: 1197 kg/m3 , 1097 kg/m3 , 1000kg/m3 , 898.2 kg/m3 and 798.4 kg/m3 ). In the experimental set-up, the pump flow capacity were varied from 12m3 /hr to 62m3 /hr at interval of 5m3 /hr and the corresponding pump power consumption, attained pump head were recorded and pump efficiency were determined. Microsoft excel was used to evaluate the trend, performance trend was used to develop the pump performance model showing the relationship between the various parameters. The results from the investigation revealed that with the various impeller sizes of 121.54mm, 109.38mm and 97.23mm of respective volute clearance of 6mm, 12mm and 18mm, the attained optimum efficiency were 74.42%, 54.78 and 33.54% respectively at a correspondence optimum pump head of 23.66m, 20.60m and 18.87m. The results also showed that there is a direct relationship between pump power consumption and process liquid density, while showing an inverse linear relationship between the pump instantaneous start up power and impeller diameter. It was therefore concluded among others that liquid with higher density will usually require higher power to initiate and maintain flow at constant flow rate and impeller size. It is then recommended among others that pump designers, application engineers and users of centrifugal pumps should consider possible increase in pump power consumption when working with a process application that has higher tendency for dynamic increase on the process fluid density.

A portable and integrated traveling-wave electroosmosis microfluidic pumping system driven by triboelectric nanogenerator

The lab-on-a-chip system can simultaneously complete the preparation, reaction, separation, and detection of samples on a centi-scale platform by manipulating trace fluids. Traveling-wave electroosmosis (TWEO) technology, with the merit of electric signal-based flexible control over the fluid behavior, can achieve precise driving of fluids, which is an important requirement of the lab-on-a-chip system. However, the peripheral power equipment such as the function generator required for TWEO limits the application in some occasions lacking power supply facilities, due to its large size and high cost. In this paper, we have developed a brand-new portable and integrated TWEO microfluidic pumping system, wherein a front-end module of triboelectric nanogenerator (TENG) is in serial connection with the back-end microfluidic pumping chip, which greatly improves portability and reduces costs. The TENG can output stable four consecutively 90°-phase-shifted alternating current voltage signals in a continuous rotational motion originated by its novel electrode structure. And the four-phase traveling potential waves are applied to four sets of electrode strips alternately distributed in the microchannel, thereby inducing nonlinear electroosmotic slip on the electrode surface, achieving stable pumping of fluids in the microchannel. Compared with traditional fluid-driven methods, this system features high safety for the operator and chip but also realizes the almost instantaneous start, stop, and directional switching in response to a turn on, turn off, and turn in reverse of TENG, respectively. Finally, this system is integrated into a droplet microfluidic chip for the efficient generation of single emulsion droplets. This study presents a promising solution for the miniaturization, integration, and commercialization of lab-on-a-chip system.

IMPACT OF SOLID BOUNDARIES AND VISCOSITY OF THE MEDIUM ON THE CONTRIBUTION OF THE INERTIAL AND VORTEX COMPONENTS OF THE NORMAL FORCE OF A ROTATING PLATE. PART 2

Within the framework of the improved method of discrete vortices, generalized for viscous media, a method has been developed for determining the contribution of forces of inertial, vortex and circulation nature to the normal force of a plate moving in a stationary viscous boundless medium accord- ing to an arbitrary law, in the presence of a wall and in a channel. The developed method was tested for the case of instantaneous angular start of the plate and subsequent constant angular speed of rotation (Wagner's problem) in a viscous boundless medium, in the presence of a wall and in a channel, in laminar and turbulent modes. The application of approximate analytical formulas for the components of the induced velocity from a discrete vortex in a viscous medium near the wall and in the channel made it possible to obtain velocity fields that visualize two vortices separated from the edges of the plate and the dynamics of their dispersion in laminar and turbulent regimes of rotation of the plate near the wall and in the channel. The inertial- vortical nature of the normal force of the plate (with the dominance of inertial forces) is confirmed, which rotates after an instantaneous start with the separation of the flow from both its edges, regardless of the presence of solid boundaries and laminar or turbulent flow regimes. It was found that in the case of the laminar regime, the effect of the presence of the wall on the reduced inertial component of the normal force of the plate is insignificant, but the influence of the channel leads to a faster departure of the laminar vortex from the moving edge of the plate, which leads to a gradual increase in the contribution of the inertial component of the normal force of the plate up to 100 % and more when turning the plate perpendicular to the channel walls. Approximately the same happens in the case of the absence of solid boundaries, when a turbulent vortex of a larger size and intensity than the corresponding laminar one moves away from the moving edge of the plate.

IMPACT OF SOLID BOUNDARIES AND VISCOSITY OF THE MEDIUM ON THE CONTRIBUTION OF THE INERTIAL AND VORTEX COMPONENTS OF THE NORMAL FORCE OF A ROTATING PLATE. PART 1

Within the framework of the improved method of discrete vortices, generalized for viscous media, a method was developed for determining the contribution of forces of inertial, vortex and circulation nature to the normal force of a plate moving in a stationary viscous boundless medium according to an arbitrary law, in the presence of a wall and in a channel. The developed method was tested for the case of instantaneous angular start of the plate and subsequent constant angular speed of rotation (Wagner's problem) in a viscous boundless medium, in the presence of a wall and in a channel, in laminar and turbulent modes. The inertial-vortical nature of the normal force of the plate (with the dominance of inertial forces) was confirmed, which rotates after an instantaneous start with the separation of the flow from both its edges, regardless of the presence of solid boundaries and laminar or turbulent flow regimes. It has been clarified, that in the case of the laminar regime, the influence of the presence of the wall on the reduced inertial component of the normal force of the plate is insignificant, but the influence of the channel leads to a faster departure of the laminar vortex from the front edge of the plate, which leads to a gradual increase in the contribution of the inertial component of the normal force of the plate up to 100% and more at the end of rotation plates. Approximately the same happens in the case of the absence of solid boundaries, when a turbulent vortex of a larger size and intensity than the corresponding laminar one moves away from the leading edge of the plate.

ОСОБЛИВОСТІ МАТЕРИНСТВА ТА ДИТИНСТВА У ПЕРІОД ВІЙНИ: СОЦІАЛЬНО-ФІЛОСОФСЬКИЙ АНАЛІЗ

Mother and child are unique structures whose connection is socially and biologically determined, as well as necessary for their full existence. The article considers the peculiarities of the situation of motherhood and childhood during the war, from the point of view of philosophical science, on the example of the war in Ukraine in 2022. An analysis of the literature on the location of the studied objects during the First and Second World Wars. The peculiarities of women’s reproductive health during the war have been studied on the example of historical references from the siege of Leningrad. The peculiarities of the psychological state of children who have experienced war have been identified, and the prospects for the development of such children have been described. Categories of children who received «war trauma» have been developed. The family in wartime is a mirror of the dynamic processes in society. Parental or maternal instinct – is essential in ensuring the viability of children. Mature maternal identity is able to ensure the harmonious existence of two personalities – mother and child. The concept of PTSD is studied. The mechanisms of stress on the human body as a balanced biological system are described. Philosophical approaches to the issue of death and war are studied. Death is considered the most mysterious phenomenon of philosophical thought, which is considered taboo in society. In terms of historical retrospect, the attitude to death is changing, which is a natural result of the development of science. War is seen as a controversial component of society, but with mostly negative consequences in both social and economic aspects. Paying attention to the devastating consequences of any war, both material and psycho-emotional, one can find archaic origins. The fear of war is a reflection of the deep fear of death. Peculiarities of philosophical concepts concerning the phenomenon of care are analyzed. Recommendations for the upbringing of a positive personality of a child during the war are given. Conclusions are drawn about the consequences of each war for any community. War, in a broad sense, is an instantaneous start of dynamic processes in society, which is expressed in all areas of human life. The worst damage to war is to children. From an early age, children can store and interpret memories of past events, and thus become aware of the surrounding reality. The mother is a key resource for the child’s sense of security, as well as a guarantee of its comprehensive and harmonious development, even in times of war.

Analytical Model of the Two-Mass Above Resonance System of the Eccentric-Pendulum Type Vibration Table

The article deals with atwo-mass above resonant oscillatory system of an eccentric-pendulum type vibrating table. Based on the model of a vibrating oscillatory system with three masses, the system of differential equations of motion of oscillating masses with five degrees of freedom is compiled using generalized Lagrange equations of the second kind. For given values of mechanical parameters of the oscillatory system and initial conditions, the autonomous system of differential equations of motion of oscillating masses is solved by the numerical Rosenbrock method. The results of analytical modelling are verified by experimental studies. The two-mass vibration system with eccentric-pendulum drive in resonant oscillation mode is characterized by an instantaneous start and stop of the drive without prolonged transient modes. Parasitic oscillations of the working body, as a body with distributed mass, are minimal at the frequency of forced oscillations.

Flexible grippers for industrial robots – comparison of features of low-cost 3D printed component

The aim of presented work was to analyse the feasibility of using 3D-print technology in robotics based on the production of industrial robot flexible grippers. For selected geometry of gripper single finger available 3D printing techniques has been analysed. The study made by authors uses the following additive technologies and devices: SLS (Selective laser Sintering) and FDM (Fused deposition modelling). As a prior an analyses of capabilities of individual technologies were done by testing the quality of the 3D CAD model recreated on test print-outs. Based on the printed gripper, its functionality, and strength properties were examined. Strength of grapplers was tested with a use of an MTS test machine under repeating deflexion simulating standard operational cycle of a gripper. Test proved that at least few thousands of cycle are possible to be made by a 3D printed gripper. What interesting gripper made with use of the less advanced printer showed different wear behaviour than an one made on the more advanced. First one showed almost instantaneous start of slow and constant strength degradation while the second one proved to have a stable deflexional capability by almost twice an number of cycles. More isotropic structure of an SLS printed gripper caused the best results of all tested ones.

A Magnetic Induction-Based Highly Dynamic Rotational Angular Rate Measurement Method

A magnetic induction-based angular rate measurement method is proposed to address the need for internal measurement of high-speed angular rate of carriers. This method relies on the rotational periodicity fed back by the magnetic field. Three coils aligned orthogonal one to another are employed as the feedback module that supplies the rotational periodicity information, the physical characteristic that contains the periodic signals, which in turn reflect the highly dynamic rotation of the carrier in its accelerating process. The periodic, instantaneous start point is extracted from the magnetic signal using zero-phase threshold technique, whereby the signal periodicity is established, enabling experimental measurement of the rotational angular rate of a high-speed rotation object. A semi-physical simulation was conducted at different speeds using a low maximum speed high-precision rotary table, and the results demonstrate that this measurement method is capable of measuring angular rate varying dynamically between 1 and 100 r/s, with a measurement error within 2‰ of the full scale. This method also provides a means for evaluating angular rate of other types of rotational movement.

An inviscid model for unsteady flow in multiply connected domains

An analytical approach is followed to model unsteady two-dimensional flow fields in multiply connected domains. The inviscid model developed here, capable of determining unsteady flows, is applied to investigate the instantaneous start of biplane configurations, including both unstaggered and tandem arrangements, and a rod–aerofoil system. Following recent advancements of two-dimensional flow modelling via conformal mapping of multiply connected domains, the so-called Schottky–Klein prime function is employed; it is the key function to construct complex potentials associated with multiple objects in the presence of free stream and vortices. In order to generate the complex potential associated with moving objects in a doubly connected domain, which is in the form of Laurent series, both impermeability and compatibility conditions are applied to evaluate boundary values of the stream function of two bodies. The strengths of vortices generated to keep the regularity of the velocity field are determined by imposing the classical Kutta condition. Consequently, wake patterns associated with the unsteady motions of biplanes and rod–aerofoil interactions are predicted with concomitant quantification of the circulation developed around the aerofoils as facilitated by the Kelvin circulation theorem.

Evolution of the Flow Field around a Circular Cylinder and a Sphere upon Instantaneous Start with a Supersonic Velocity

Evolution of the flow field around a circular cylinder and a sphere instantaneously starting with a constant supersonic velocity (M∞ = 5 and Re = 105) from the state at rest is studied by means of numerical integration of unsteady two‐dimensional Navier–Stokes equations.

Microscopic Modeling of Vehicle Start Emissions

A microscopic framework for estimating instantaneous vehicle start emissions for light-duty vehicles and trucks is developed. The framework assumes a linear decay in instantaneous start emissions over a 200-s time horizon. The initial vehicle start emissions rate is computed by using the soak time function of the U.S. Environmental Protection Agency’s MOBILE6 model, assuming a 200-s decay time interval. The use of the MOBILE6 soak time function ensures that the microscopic procedures that are developed produce start emissions that are consistent with the MOBILE6 model. The validity of the framework was demonstrated using independent trips that involved cold-start and hot-start impacts with vehicle emissions estimated to within 10% of the test in-laboratory measurements.

Temporal reasoning using tesseral addressing: towards an intelligent environmental impact assessment system

A temporal reasoning system is described which uses a tesseral addressing referencing system. The tesseral addressing techniques used are directly compatible with raster based Geographic Informatiori Systems (GIS) and by extension vector based GIS. As a result the temporal reasoning mechanism can be integrated into GIS systems and provide a temporal reasoning capability for such systems. Although the target application of the system described is the production of Environmental Impact Assessment reports it is considered that the advantages offered have a much wider field of application. The temporal reasoning approach advocated has similarities with Kowalski's event calculus in that the principal entities under consideration are temporally displaced events which have temporal attributes associated with them. Events are considered to be instantaneous; non-instantaneous events are described in terms of instantaneous start and end events. The temporal attributes which can be associated with events comprise sets of one or more ranges. Ranges may define a time period during which an event can be said to occur, in which case they are defined in terms of their earliest and latest times (tesseral address), or they may be used to allocate an absolute reference to an event, i.e. a range comprising a single tesseral address. Experiments to date have indicated that the system provides an excellent foundation on which to base further, multi-dimensional reasoning, work.

Soft Start of Submersible Pumped Oil Wells

Cyclic operation of submersible pumping is considered undesirable because of the start-stop characteristics of the installation. ''Across-the-line'' starting results in large current surges, typically five to eight times running current. Such surges can damage the motor and its cable and also cause line voltage irregularities. Also, stopping can result in significant amperage and voltage spikes. Because of this, most operators are very reluctant to start and stop a submersible pumping installation any more often than absolutely necessary. This creates design problems in sizing the pump. Reduced-voltage starting should minimize the severe strain imposed on the electrical system by an instantaneous start. A reduced-voltage solid-state starter using six silicon-controlled rectifiers was tested between Nov. 1981 and March 1982. The current surge on start was limited to about 2.5 times full-load amperage. The time required to bring the motor to full speed was increased from about 0.25 seconds to 1.3 seconds. The well was cycling on-off about six times per day. The unit was start-stopped about 900 times during the test. A prototype production model is available.

Formation of a region of interaction and of a wake with the instantaneous start of a plate in an incompressible liquid

The flow arising in an incompressible liquid if, at the initial moment of time, a plate of finite length starts to move with a constant velocity in its plane, is discussed. For the case of an infinite plate, there is a simple exact solution of the Navier—Stokes equations, obtained by Rayleigh. The case of the motion of a semiinfinite plate has also been discussed by a number of authors. Approximate solutions have been obtained in a number of statements; for the complete unsteadystate equations of the boundary layer the statement was investigated by Stewartson (for example, [1–3]); a numerical solution of the problem by an unsteady-state method is given in [4]. The main stress in the present work is laid on investigation of the region of the interaction between a nonviscous flow and the boundary layer near the end of a plate. In passing, a solution of the problem is obtained for a wake, and a new numerical solution is also given for the boundary layer at the plate.

Performance of Otto Engine by Extremely Rich Mixture of Methane-Oxygen

Natural gas is generally used as raw material for chemical industry as well as for fuel of internal combustion engine. Hence, the power output and the composition of exhaust gas were calculated by assuming the ideal Otto cycle, and compared its result with that obtained by modified CFR engine supplied by extremely rich mixture of Methane-Oxygen.According to the results of experiment, the exhaust gas was mainly composed of hydrogen and carbon monoxide, both necessary for synthetic gas at the maximum percentage of 61 and 42 respectively and power output up to 1.5kWhr/m3 of methane was obtained which was able to produce necessary oxygen.The power output was considerably small due to the extremely rich mixture but the engine ran smoothly in spite of pure oxygen and any abnormal combustion was not marked even in the indicater diagram by Piezo Type Indicator. The amount of formation of free carbon was negligibly small, which made the exhaust gas almost colorless. Almost no carbonaceous deposit was observed on the surface of combustion chamber after repeated intermittent runnings for a long time.If the combustion chamber of the internal combustion engine were used for chemical reactor, it was considered to be an excellent compact one having the ability of instantaneous start and stop, since the control of the reaction was simple and reliable.